The invention relates to a machine tool for the turning of workpieces with eccentric sections, comprising a tool support movable in the direction of at least one axis, a workpiece spindle drivable for rotation about a spindle axis and comprising a workpiece chuck, in which the workpiece can be clamped with a variably adjustable eccentricity, wherein the workpiece chuck has a chuck housing, a collet actuation and a collet support arranged in the chuck housing and having a collet held thereon, this collet being adapted to be brought into concentric or eccentric positions relative to the spindle axis as a result of movement of the collet support relative to the chuck housing.
A machine tool of this type is known from the state of the art but, in this case, a stepless adjustment of the collet support relative to the chuck housing can be adjusted only manually, in particular, using measuring tools for the exact determination of the eccentricity of the respective adjustable position.
The object underlying the invention is therefore to improve a machine tool of the generic type in such a manner that the adjustment of the collet support relative to the chuck housing can be brought about more simply.
This object is accomplished in accordance with the invention, in a machine tool of the type described at the outset, in that the machine tool has at least one axis controlled by a machine control, that an adjusting element is provided on the machine tool and this element can be moved towards the workpiece chuck for the adjustment of the respective adjustable position of the collet and can be brought into operative connection with a receiving means connected to the collet support and that in this operative connection between the adjusting element and the collet support the relative movement between the collet support and the chuck housing for the alteration of the adjustable position can be controlled by means of the machine control by way of the at least one controlled axis.
The advantage of the inventive solution is to be seen in the fact that with it it is possible to use the machine control, which is generally present in any case, to carry out the respective adjustable position of the collet relative to the chuck housing so that, on the one hand, the complicated manual adjustment can be dispensed with and, on the other hand, there is even the advantage that during a machining cycle a variation of the adjustable position is possible by means of corresponding specifications of the machine control.
This may be achieved particularly favorably when the adjusting element can be moved by the machine control relative to the receiving means in a direction of engagement which extends transversely to the direction of movement of the collet support relative to the chuck housing.
As a result of a direction of engagement extending in such a manner the adjusting element and the receiving means may be designed as interacting form-locking elements which can be brought into engagement with one another simply due to the movement in the direction of engagement in order to provide the connection between the adjusting element and the collet support.
In principle, the direction of engagement can always be aligned in different directions. In this respect, a solution which is particularly favorable with respect to the conditions in a machine tool provides for the direction of engagement to extend approximately parallel to the spindle axis.
In principle, it would be conceivable to move not only the collet support relative to the chuck housing during the adjustment of the adjustable position but, at the same time, to move the chuck actuation with it in order to be able to keep the workpiece clamped in the collet in an unchanged manner even during variation of the adjustable position.
This is constructionally complicated.
For this reason, one advantageous solution provides for the workpiece chuck to have an actuating element which can be actuated at least indirectly by the machine control and with which the collet actuation can be acted upon in the direction of a holding position of the collet still holding the workpiece in the collet.
This means that with this solution the clamping of the workpiece in the collet is not brought about in the customary manner, i.e., with the customary cocking cylinder since the forces applied by the cocking cylinder and normally required for a secure clamping during the machining are so great that an adjustment of the collet support relative to the chuck housing is no longer possible with any justifiable expenditure of force.
For this reason, the customary cocking cylinder is deactivated for the adjustment of the collet support relative to the chuck housing and only the collet actuation is acted upon in such a manner that the workpiece is still held by the collet in its position relative to the collet and is not released in it.
For example, it would be conceivable for this purpose to provide an additional cocking cylinder to the customary cocking cylinder as actuating element which is in a position to apply such a small clamping force which still allows the workpiece to be fixed in position in the collet but, at the same time, the collet support to also be moved relative to the chuck housing.
This solution is constructionally complicated. For this reason, a simplified solution provides for the actuating element to be actuatable due to action on the workpiece chuck from outside.
Such action on the workpiece chuck from outside can be brought about in the most varied of ways. For example, it would be conceivable to provide a separate actuating device outside the workpiece chuck which acts on the actuating element in a defined position of the workpiece chuck.
A simple possibility for realizing such an actuating device provides for this to be formed by the tool support so that the actuating element can be actuated by the tool support.
Since, in the inventive sense, the workpiece chuck must be acted upon in any case by means of the adjusting element in order to adjust the collet support relative to the chuck housing, a particularly preferred embodiment provides for the actuating element to also be actuatable by the adjusting element.
A particularly favorable solution provides for the actuating element to be arranged on the collet support and to be movable together with it during the alteration of the adjustable position relative to the chuck housing so that the actuating element co-migrates during the movement of the collet support relative to the chuck housing due to the adjusting element and thus can also be coactuated by the adjusting element.
Fundamentally, it would be conceivable for the adjusting element to act on the inventive workpiece chuck in two ways, namely, on the one hand, on the receiving means and, on the other hand, on the actuating element.
A solution which is particularly favorable from a constructional point of view provides for the actuating element to bear the receiving means for the adjusting element so that the adjusting element can come into operative connection with the receiving means in a particularly simple manner and, at the same time, can actuate the actuating element.
An expedient construction therefore provides for the actuating element to be movable in the direction of engagement of the adjusting element so that as a result of movement of the adjusting element in the direction of engagement an actuation of the actuating element is brought about at the same time in order to act on the collet actuation.
In this respect, it has proven to be particularly favorable from a constructional point of view when the actuating element is movable approximately parallel to the spindle axis.
With respect to the arrangement of the adjusting element on the inventive machine tool, the most varied of possibilities are conceivable. For example, it would be conceivable to provide a separate moving device for the adjusting element.
However, a solution which is particularly favorable from a constructional point of view provides for the adjusting element to be held on the tool support movable by the machine control so that the axes provided for the tool support and controllable by the machine control are available at the same time as axes of movement for the movement of the adjusting element.
In this respect, it would be conceivable to arrange the adjusting element on the tool support in addition to the tool. A particularly favorable solution provides, however, for the adjusting element to be arranged in the tool support instead of a tool.
In this respect, the tool support can be designed as a single tool support and the adjusting element can be interchanged each time for a tool when the adjusting element is required.
However, it is also conceivable to design the tool support as a multiple tool support, for example, as a tool turret and to equip one tool station with the adjusting element at least when an alteration in the adjustable position of the collet relative to the chuck housing is imminent.
The inventive concept may be realized particularly favorably when the tool support is movable by the machine control in the direction of engagement of the adjusting element.
Furthermore, it is favorable when the tool support is movable by the machine control transversely to the direction of engagement of the adjusting element so that the adjusting element may be aligned relative to the receiving means in a simple manner in order to act on the receiving means.
A particularly advantageous embodiment provides for a securing of the collet support in position relative to the machine base to be achievable by means of the adjusting element and for the relative movement between the chuck housing and the collet support to be achievable by means of a rotation of the workpiece spindle about the C axis controlled by the machine control.
This solution provides for the C axis of the workpiece spindle to be utilized for varying the adjustable position of the collet support relative to the chuck housing while the adjusting element merely serves to secure the collet support relative to the machine base.
This solution offers itself, in particular, when the collet support is mounted in the chuck housing for rotation about an axis eccentric to the spindle axis.
This solution can, however, also be realized when the collet support is mounted so as to be linearly displaceable in the chuck housing.
Another advantageous solution provides for a movement of the collet support relative to the chuck housing to be achievable by means of the adjusting element, when the workpiece spindle is stationary in that the collet support is movable by means of an axis controllable by the machine control and moving the adjusting element relative to the chuck housing, i.e. the adjusting element is movable, for example, relative to the chuck housing by means of the tool support movable along at least one axis.
The invention also relates to a workpiece chuck for a tool spindle of a machine tool rotatable about a spindle axis.
The object specified at the outset is accomplished in accordance with the invention, in a workpiece chuck of this type for a tool spindle of a machine tool rotatable about a spindle axis, in which the workpiece can be clamped with adjustable eccentricity in relation to the spindle axis, wherein the workpiece chuck has a chuck housing, a collet actuation and a collet support arranged in the chuck housing and having a collet held in it, this collet being adapted to be brought into concentric or eccentric adjustable positions relative to the spindle axis as a result of movement of the collet support relative to the chuck housing, in that a receiving means is provided on the collet support for the adjustment of the adjustable positions of the collet, this receiving means being adapted to be brought into operative connection with an adjusting element of the machine tool so that in this operative connection between the adjusting element and the collet support the relative movement between the collet support and the chuck housing for altering the adjustable position can be brought about.
The advantage of the inventive solution is thus to be seen in the fact that with it action on the workpiece chuck is possible in a simple manner in order to adjust the collet support relative to the chuck housing.
For example, the operative connection between the receiving means and the adjusting element could be brought about by means of a force-locking connection, for example, clamping of the receiving means by the adjusting element. It is, however, particularly favorable when the operative connection between the receiving means and the adjusting element is brought about by way of form locking.
A particularly expedient solution provides for the form-locking connection of adjusting element and receiving means to be achievable by means of a relative movement in a direction of engagement which extends transversely to the direction of movement of the collet support relative to the chuck housing.
Adjusting element and receiving means may be brought into operative connection particularly expediently when the direction of engagement extends approximately parallel to the spindle axis.
In conjunction with the embodiments of the inventive workpiece chuck explained thus far, details have been given only on the adjustment of the collet support relative to the chuck housing.
In order to be able to carry out an adjustment of the collet support relative to the chuck housing with a justifiable expenditure of force it is necessary to release the customary action on the collet by means of the cocking cylinder since the forces generated by the cocking cylinder for clamping the workpiece by means of the collet prevent any movement of the collet support relative to the chuck housing with a reasonable expenditure of force.
When the clamping of the workpiece in the collet is released, this can become loose in the collet and, in particular, the positioning of the workpiece relative to the collet and thus relative to the workpiece spindle may be altered so that the precision of the machining is lost.
For this reason, it is provided in a particularly advantageous embodiment of the inventive workpiece chuck for the collet actuation to be acted upon in the direction of a holding position of the collet still holding the workpiece in the collet during the relative movement between the collet support and the chuck housing.
This could, for example, be achievable in that an additional cocking cylinder or an additional step of the available cocking cylinder is provided which allows clamping of the workpiece by means of the collet with a small clamping force.
The clamping force is preferably determined such that the workpiece is still held securely in the collet without any machining.
In this respect, the clamping force is preferably smaller than approximately 5%, preferably smaller than approximately 1%, even better approximately 0.5% of the customary clamping force.
Another solution provides, for example, for an elastic biasing means which sees to it even when the cocking cylinder is disengaged that the collet actuation still acts on the collet with an adequately large force in order to still hold the workpiece securely in a clamped manner without any machining.
A particularly preferred solution provides for the workpiece chuck to have an actuating element which can be actuated from outside the same and with which the collet actuation can be acted upon in the direction of a holding position of the collet still holding the workpiece in the collet.
As a result of such an actuating element it is possible to act on it in a concerted manner and thus to still hold the workpiece securely in the collet in a concerted manner when a relative movement of collet support and chuck housing is intended to take place.
A particularly advantageous design of the inventive workpiece chuck provides for the actuating element to be actuatable as a result of action on the workpiece chuck from outside.
Since action on the workpiece chuck by means of the adjusting element is, in any case, necessary for varying the adjustable position, a particularly favorable solution provides for the actuating element to be actuatable by means of the adjusting element.
In order to be able to carry out such an actuation by means of the adjusting element, it has proven to be particularly favorable when the actuating element is arranged on the collet support and is movable together with it during the alteration of the adjustable position relative to the chuck housing so that during the adjustment of the collet support the moving element can be acted upon at the same time in a simple manner.
In principle, it would be conceivable to act with the adjusting element in two ways, namely, on the one hand, on the actuating element and, on the other hand, on the receiving means. It is, however, particularly favorable when the actuating element bears the receiving means for the adjusting element so that any action on the receiving means corresponds at the same time to an action on the actuating element.
The actuating element can be acted upon by means of the adjusting element in a particularly simple manner when the actuating element is mounted for movement in the direction of engagement of the adjusting element.
A solution, with which the actuating element is movable approximately parallel to the spindle axis, may be realized particularly advantageously from a constructional point of view.
With respect to the type of movability of the collet support relative to the chuck housing, no further details have so far been given. For example, one advantageous solution provides for the collet support to be rotatable in the chuck housing about an axis which is arranged eccentrically but parallel to the spindle axis and for the collet to be arranged with its axis of symmetry eccentrically but parallel to this axis.
As a result, it is possible to vary the distance between the axis of symmetry and the spindle axis by turning the collet support relative to the chuck housing and thus to arrange the collet in different concentric or eccentric adjustable positions relative to the spindle axis.
Alternatively thereto, a different solution provides for the collet support to be displaceable linearly in the chuck housing so that as a result of linear displacement of the collet support the collet can either be arranged concentrically to the spindle axis or can be arranged eccentrically in the direction of two oppositely extending directions, wherein the axis of symmetry of the collet always extends parallel to the spindle axis.
The inventive workpiece chuck may be used particularly expediently when this is used in a machine tool corresponding to any of the embodiments described above.